1. Field of the Invention
The present invention relates to improvements in an X-ray apparatus for medical diagnosis, for example, dental and otolaryngological diagnosis, and more particularly to improvements in an X-ray apparatus for photographing planigraphic planes.
2. Prior Art
X-ray apparatuses for photographing tomographic planes of human heads, faces and jaws are known for medical diagnosis, for example, dental and otolaryngological diagnosis. In particular, rotational tomographic X-ray apparatuses for photographing dental arches have been used widely at small dental clinics as dental panoramic X-ray apparatuses. These days, in addition to the rotational tomographic X-ray apparatuses, there is an increase in demand for planigraphic X-ray apparatuses capable of selectively photographing specific regions, such as temporomandibular joints and dental implants, at narrow tomographic widths.
In view of increasing demands, the applicant of the present invention has proposed a rotational tomographic X-ray apparatus with a planigraphic function as Japanese Patent Application No. 4-139888 (Japanese Laid-Open Patent Publication No. 6-181). This apparatus is basically the panoramic X-ray apparatus additionally equipped with a planigraphic function. The apparatus is capable of performing clear planigraphic photographing without causing any distortion, equipped with a function for changing the magnifying ratios of X-ray images and is relatively compact and inexpensive enough to allow easy introduction to small clinics.
To perform planigraphic photographing, it is necessary to dispose an X-ray generator and an X-ray detection surface disposed opposite to each other with a subject positioned therebetween while maintaining a constant relationship, and to move the X-ray generator and the X-ray detection surface in parallel to the planigraphic plane selected to be photographed inside the subject and in directions opposite to each other. For this purpose, in the proposed apparatus, a rotary arm supporting the X-ray generator and the X-ray detection surface is linearly moved by using a position adjustment mechanism such an X-Y table provided for the panoramic X-ray apparatus, or the rotary arm is moved together with a position adjustment mechanism and an arm rotation mechanism as a whole system by using a linear movement mechanism of a different type.
However, when using a position adjustment mechanism, it is necessary to place the subject, or patient, in a predetermined direction in view of the directions of the position adjustment mechanism and the planigraphic plane to be photographed so as to move the X-ray generator and the X-ray detection surface in parallel with the planigraphic plane. This makes the first setting of the apparatus troublesome. Even though the movement parallel to the planigraphic plane can be obtained by placing the patient in a given direction and by combining the movements of the position adjustment mechanism in all dimensions, the control program to be used for this case becomes very complicated. In the case of a whole system which is moved by using a linear mechanism of a different type, the weight of the movable section becomes large, thereby causing the problems of making the linear movement mechanism large and expensive.